OBJECTIVE
Our objective was to utilize a large extensively-typed ethnically-homogeneous set of IDDM families to investigate the relationship of alleles at loci in the HLA region to IDDM susceptibility. In particular, we wanted to examine the effects of DR alleles, since a recent study (Thomson 1984) suggested, although no test of significance was applied, that alleles other than DR3 and DR4 have non-neutral effects on susceptibility. THE DATA Data were available on 169 German IDDM families, most of them simplex, from a cooperative study of J. Bertrams and M. P. Baur (dataset "1DDM.GER"). Almost all family members were typed for HLA-A, B, C, DR and GLO, and the majority were also typed for C2, C4A, C4B, and BF.
Using this information, we haplotyped all individuals. In the few cases where there was uncertainty about whether a person was homozygous for a particular allele or heterozygous with a "blank" allele , the ambiguous allele was coded as missing data and thus omitted from the analyses.
We then assigned the four independent parental haplotypes of each family to one of two groups: 1) the "diabetic" group, if the haplotype occurred in any diabetic in the family, or 2 ) the "non-diabetic" group, if the haplotype did not occur in any diabetic in that family.
Since recombinant haplotypes are not independent, they were omitted from the analyses. If a recombinant occurred in a diabetic, the two parental haplotypes giving rise to the recombinant were also omitted, as they could not be classified in one or other group.
The "non-diabetic"